We investigate the gas phase proton transfer reactivity of the dianionic molybdenum oxysulfide clusters [Mo₂O₂S₆]^2– and [Mo₂O₂S₅]^2– in binary collisions in an FT-ICR mass spectrometer in combination with quantum chemical calculations. The proton transfer reactions are probed with a series of acids with increasing proton affinity, namely trifluoroacetic acid, difluoroacetic acid, pyruvic acid and formic acid. Proton transfer followed by Coulomb explosion is observed for both dianions with all acids except for formic acid. The calculations predict a proton affinity of 16.1(1) and 16.5(1) eV for [Mo₂O₂S₆]^2– and [Mo₂O₂S₅]^2–, respectively, significantly higher than the proton affinities of tri- and difluoroacetate as well as pyruvate and formate, which range from 14.00(18)–14.98(10) eV. Calculated reaction potential energy surfaces explain the observations. A Coulomb barrier separating the collision complex from the products is present in all cases. The barrier lies well below the entrance channel for trifluoroacetic acid, difluoroacetic acid and pyruvic acid. For formic acid, however, the barrier lies near the entrance channel.

我们在FT-ICR质谱仪结合量子化学的基础上，研究了二元碰撞中的二价氧化钼钼簇[Mo ₂ O ₂ S ₆ ] ^2–和[Mo ₂ O ₂ S ₅ ] ^2–的气相质子转移反应性。计算。用一系列具有增加的质子亲和力的酸（即三氟乙酸，二氟乙酸，丙酮酸和甲酸）探测质子转移反应。对于两种带有除甲酸以外的所有酸的双阴离子，均观察到了质子转移并随后发生库仑爆炸。计算预测[Mo ₂ O的质子亲和力为16.1（1）和16.5（1）eV。₂ S ₆ ] ^2–和[Mo ₂ O ₂ S ₅ ] ^2–分别显着高于三氟乙酸酯和二氟乙酸酯以及丙酮酸和甲酸的质子亲和力，其范围为14.00（18）–14.98（10） eV。计算出的反应势能面解释了这些观察结果。在所有情况下均存在将碰撞复合物与产物分离的库仑屏障。屏障位于三氟乙酸，二氟乙酸和丙酮酸的入口通道下方。但是，对于甲酸，屏障位于入口通道附近。